Node.JS and Postgres Search Bar

first of all, congrats for starting a new studies task! But let's solve this issue, shall we?

1 - My tip for you, is that before you even start to worry about the frontend, let's make sure that our service is running fine, and we shall test it on the server-side only. "I think I am connected to my database", we cannot proceed if we think something is going on fine, we need to make sure!

2 - We need our service running, that`s the only way we can get our DB connected. So for now, we forget about the interface and DB, let's focus on the service: Inside your "app.js" you are trying to import your routes right? By doing

const routes = require('./server/routes/index');

But in order to do that, you need to export those routes before, then go to your "index.js" file and add "module.exports = router". Now you can use your router imported inside your "app.js" file!

Stays like this:

const express = require('express');
const router = express.Router();
const pg = require('pg');
const path = require('path');
const connectionString = process.env.DATABASE_URL || 'postgres://postgres:postgres@localhost:5432/todo';

 Almost there, our service needs to listen to some port now


router.get('/', (req, res, next) => {
  res.sendFile(path.join(
    __dirname, '..', '..', 'client', 'views', 'index.html'));
});

router.get('/api/v1/todos', (req, res, next) => {
  console.log("HAHAHAHAHA")
  const results = [];
  // Get a Postgres client from the connection pool
  pg.connect(connectionString, (err, client, done) => {
    // Handle connection errors
    if(err) {
      done();
      console.log(err);
      return res.status(500).json({success: false, data: err});
    }
    // SQL Query > Select Data
    const query = client.query('SELECT name FROM world_heritage_sites.caravanserai ORDER BY iso ASC;');
    // Stream results back one row at a time
    query.on('row', (row) => {
      results.push(row);
    });
    // After all data is returned, close connection and return results
    query.on('end', () => {
      done();
      return res.json(results);
    });
  });
});

module.exports = router;

Now our application needs to listen to some port. I don't have access to your folder structure, that's why I will work the idea using only these two files you presented us. Inside your "app.js" you got tell your application to serve using one port, you can do that by typing "app.listen(8000, () => console.log('listening')) " since you are exporting your app, you can import and use it anywhere you'd like, but I told you already, I will work the idea restricted to the files you showed us, that's why your "app.js" would be like this check this Docs before : https://node-postgres.com/features/connecting

const express = require('express');
const path = require('path');
const logger = require('morgan');
const cookieParser = require('cookie-parser');
const bodyParser = require('body-parser');
const routes = require('./index');
// var users = require('./routes/users');

const app = express();

// view engine setup
// app.set('views', path.join(__dirname, 'views'));
// app.set('view engine', 'html');

// uncomment after placing your favicon in /public
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'client')));

app.use('/', routes);
// app.use('/users', users);

// catch 404 and forward to error handler
app.use((req, res, next) => {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// error handlers

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
  app.use((err, req, res, next) => {
    res.status(err.status || 500);
    res.json({
      message: err.message,
      error: err
    });
  });
}

// production error handler
// no stacktraces leaked to user
app.use((err, req, res, next) => {
  res.status(err.status || 500);
  res.json({
    message: err.message,
    error: {}
  });
});


app.listen(8000, () => console.log('listening'))

module.exports = app;

Ok, now our service is running, go to your terminal and type: node app.js

it should print "listening" in your shell.

Now try to access http://localhost:8000/api/v1/todos in your browser, it should print an error "pg.connect is not a function"

That's because you are not using the lib the right way, try something like this

const express = require('express');
const router = express.Router();
const path = require('path');
const { Pool, Client } = require('pg')
const connectionString = 'postgres://postgres:postgres@localhost:5432/todo'
const client = new Client({
  connectionString: connectionString,
})
client.connect()

router.get('/', (req, res, next) => {
  res.sendFile(path.join(
    __dirname, '..', '..', 'client', 'views', 'index.html'));
});

router.get('/api/v1/todos', (req, res, next) => {
  const results = [];
  client.query('SELECT name FROM world_heritage_sites.caravanserai ORDER BY iso ASC;', (err, res) => {
    console.log(err, res)
    client.end()
  })
});

module.exports = router;

But remember, you need to have your Postgres service running in your localhost to connect using this connection string you are using. If you configured your Postgres service and db the right way, it should work fine, then you just need to call your route "localhost:8000/api/v1/todos" in your interface.

Actually there are a lot of things you should check in your code, and maybe it's good if you get some background before start this project. Try some tutorials for beginners on youtube and check other dev's code. Good Luck and Good code dude! I hope I gave you at least a little help :)